Explosive composition comprising alkali metal nitrate, ammonium nitrate and halogenated hydrocarbon



United States atent 3 264 151 EXPLOSIVE coMPosiriois COMPRISING ALKALI METAL NITRATE, AMMONIUM NITRATE AND HALOGENATED HYDROCARBON Oliver Osborn, Charles F. Schrieber, and James R. Mm-

derhout, Lake Jackson, Tex., assignors to The Dow Chemical Company, Midland, Mich a corporation of Delaware No Drawing. Filed Mar. 26, 1964, Ser. No. 355,089

6 Claims. (Cl. 149-41) This invention relates to explosives and more particularly is concerned with a novel, high density, waterresistant inorganic nitrate containing explosive composition.

It is a principal object of the present invention to provide a water-resistant explosive based on inorganic nitrates.

It is another object of the present invention to provide an inexpensive, substantially water-proof explosive which has a density greater than about 1 gram per cubic centimeter and is readily deformable so as to conform to the irregular geometry ordinarily associated with borehole walls.

It is a further object of the present invention to provide a novel system of relatively dense explosive blasting agents utilizing substantially water immiscible halogenated hydrocarbons as essential components.

These and other objects and advantages readily will become apparent from the detailed description presented hereinafter.

Unexpectedly, it has been found in the present invention that substantially water immiscible halogenated liquid hydrocarbons in combination with alkali metal nitrates and ammonium nitrate fonn water-resistant explosive compositions of density greater than 1 gram per cubic centimeter.

The present novel composition comprises a substantially water immiscible halogenated aliphatic hydrocarbon having a density of at least about 1.2 grams per cubic centimeter and a carbon chain length of from about 1 to about 3 blended with a mixture of ammonium nitrate and alkali metal nitrate. The amount of substantially water immiscible halogenated hydrocarbon fuel ranges from about 5 percent up to about 25 percent, based on the total composition weight, and at a maximum is further characterized as being such that the resulting composition is stoichiometrically balanced with respect to the fuel-oxidizer mixture. Further, depending on the amount of halogenated hydrocarbon, the resulting composition will range in physical characteristics from blends showing water resistance (lower levels of halogenated organic) to those which are substantially completely water proof in nature at the higher concentrations of halogenated organic compound. The mixture of alkali metal nitrate and ammonium nitrate contains from 12 to about 65 weight percent of the alkali metal nitrate and from about to about 83 weight percent of ammonium nitrate, based on the total composition weight. The actual proportions of the inorganic nitrates in the mixture to be used in a specific formulation is determined, at least in part, by the oxygen needed for a requisite fuel-oxidizer balance.

Conveniently, the halogenated hydrocarbon is gelled or thickened with a metal salt of a long chain fatty acid or other thickening or gelling agent suitable for use with such materials. The amount of such agents ranges from about 0.2 to about 5 weight percent, based on the weight of the halogenated hydrocarbon.

Although the liquid halogenated hydrocarbon itself can be used both to impart the predetermined water resistivity or water-proof characteristics to the mixture as well as serve as a source of carbon fuel, ordinarily the halogenated hydrocarbon is blended with other carbonaceous fuels such as liquid hydrocarbons or low molecular weight alcohols, ketones, aldehydes, ethers or mixtures of these for example. The amount of such carbonaceous fuel to be used at a maximum is about 8 weight percent, based on the total composition weight. Ordinarily, if additional hydrocarbon fuel is employed, the concentration employed is within the range of from about 4 to about 6 weight percent of the total mix.

Additionally, particulated metals, as fuels and/or sensitizers, can be incorporated into the composition. The light metals, such as magnesium, aluminum or alloys and mixtures thereof as well as other metals such as iron, titanium and zirconium and the like, for example, all are satisfactory additaments for use in the composition of the present invention. If metal is incorporated into the mix, at a maximum it is an amount which on the basis of chemical and thermodynamic considerations is associated or reacted on a stoichiometric basis with the amount of water and oxygen available in the reaction products upon detonation of the composition. Usually from about 5 to about 35 weight percent metal, based on total composition weight is employed.

Other sensitizers, fuels, oxidizers and the like ingredients which do not change the nature of the present inventive composition also can be added to the composition.

In a preferred embodiment of the invention, sodium nitrate is employed as the alkali metal nitrate in conjunction With ammonium nitrate. At least a portion of these oxidizers is dissolved in water ordinarily to provide a saturated solution and at a minimum to provide a solution having about 25 weight percent solute concentration wherein the amount of said nitrate component in said solution is from about 10 to about 25 weight percent of the total explosive composition. This solution is thickened, ordinarily with a natural gum, about 0.25 to about 2.5 percent based on the aqueous solution weight, such as guar gum for example, which gum in turn is crosslinked by a small amount of aqueous ammonia solution or aqueous alkali metal dichromate solution. Carbon tetrachloride, from about 11 to about 19 weight percent of the total composition, and thickened with from about 0.5 to about 2.5 percent by weight of a metal soap, for example aluminum oleate or aluminum octoate, and having from about 4 to about 6 weight percent (based on total composition weight) of a liquid carbonaceous fuel blended therewith is admixed with the aqueous nitrate solution.

Solid particulate sodium nitrate, ammonium nitrate or mixtures thereof to provide a combination from about 20 to about 55 weight percent of the total composition is blended with the mixed liquid component along with from about 5 to about 35 Weight percent particulate.

alumin um.

-during fabrication etc.

The resulting composition is characterized in that the proportion of alkali metal nitrate/ammonium nitrate is from about 4/1 to about 1/ 1. The composition is further characterized in that the total amount of liquid present, both aqueous and organic, must be from about 35 to about 60 weight percent of the total composition so as to encompass all the solid particulate ingredients in a water resistant, and in many embodiments substantially water-proof covering, which also imparts a ready deformability and pliability to the composition.

The term alkali metal nitrate as used herein is meant to include lithium nitrate, sodium nitrate, potassium nitrate, cesium nitrate and rubidium nitrate.

Both the alkali metal nitrates and ammonium nitrate solid components of the composition can be in the form of prills, crushed prills or other particulated solid form. In general these will range in size from about 12 to about 70 mesh U.S. Standard Sieve.

Halogenated hydrocarbons suitable for use in the pres ent composition are the liquid bromo-, chlororand iodosubstituted hydrocarbons which are substantially water insoluble and have a high density i.e. greater than about 1.2 grams/ cubic centimeter. Preferably, these materials also have a heat of vaporization less than water and have a low vapor pressure at room temperature. Additionally, these must impart a water repellency to the mix and exhibit no detrimental reaction with other mix components at ambient temperatures encountered in storage, Substantially water-insoluble, halo-substituted aliphatic hydrocarbons having a carbon chain length of from 1 to about 3 as, for example carbon tetrachloride, carbon tetrabromide, trichloroethylene, ethylene dichloride, hexachloroethane, ethylene dibromide and the like all are satisfactory for use in the present invention. Carbon tetrachloride is preferred.

Gelling and thickening agents for the halogenated hydrocarbon are those materials which thicken it into a semi-jelly state when blended therewith. Alkaline earthand earth metal salts of long chain carboxylic fatty acids having a carbon chain length of from about 8 to about 24 carbon atoms ordinarily are used. Specific examples of suitable alkaline earth metaland earth metal fatty acid salts for use in the present invention are aluminum oleate, aluminum stearate, aluminum tallate, calcium stearate, calcium tallate, calcium oleate and the like. Aluminum oleate and aluminum octoate have been found to be particularly suitable. The term alkaline earth metal as used herein with respect to the .fatty acid metal salts includes magnesium, calcium, strontium and barium. The term earth metal is meant to include aluminum, gallium, indium and thallium.

Carbonaceous liquid fuels which can be used in the composition are petroleum oils and liquid fractions derived therefrom, such as fuel oil, kerosene, gasoline fractions, lubricating oils and the like, low molecular weight alcohols having from 1 to about carbon atoms, such as methanol and ethanol, low molecular weight ketones and aldehydes having from about 2 to about 5 carbon atoms such as acetone, acetaldehyde and methyl ethyl ketone, low molecular weight ethers having from about 2 to about 4 carbon atoms such as dimethyl ether, methyl ethyl ether, diethyl ether, and the like as Well as mixtures of these.

Gelling agents suitable for use with the aqueous nitrate solutions can be selected from both synthetic and natural thickeners. Natural gums such as guar gum and karawa gum usually are employed.

Aluminum metal, preferably large particulate scrap, is a preferred metal fuel. Particles up to about 1.5 inches or more in length, a thickness of from 0.0008 to about 0.08 inch and a width of from about 0.01 to about 0.5 inch are both readily available and particularly suited for use in the present composition. Other atomized, ground, flake and chip forms of the metal fuel component can be used. Preferably the particles should be of a relatively uniform distribution and contain less than about 2 weight percent particles passing a 325 mesh U.S. Standard Sieve.

It has been reported in the literature that aluminum and chlorinated hydrocarbons can undergo spontaneous, rapid, exothermic reaction. This corosion phenomenon appears to be quite temperature dependent since, for example, the corrosion rate of aluminum in the presence of carbon tetrachloride is very high at the boiling point of the perchlorocarbon. However, in actual tests at about 50 C., over a period of 60 days, only slight reaction occurred and no visible corrosion could be observed over a period of 18 months in a test run at room temperature.

Additionally it has been found that the presence of magnesium and/or magnesium alloyed with the aluminum substantially reduces the high temperature rapid corrosion rate of aluminum in CCl Apparently these alloying ingredients provide a protective oxide or other insulating layer on the metal surface. Since readily available commercial aluminum scrap normally contains either manganese or magnesium or both of these metals as alloying ingredients and usually has a protective oxide layer, such particulate material therefore has been found to be particularly compatible with the halogenated hydrocarbon ingredients of the instant explosive composition with regards to storage stability and non-degradability of the mix by chemical corrosion or reaction.

Particulate magnesium, magnesium-aluminum mixtures, magnesium alloys, aluminum alloys, coarse iron filings and the like also can be used as fuels in the present composition.

The following examples will serve to further illustrate the present invention but are not meant to limit it thereto.

Example 1.-A number of explosive compositions were prepared in accordance with the present invention using carbon tetrachloride, aluminum octoate or aluminum oleate, methanol, ammonium nitrate, sodium nitrate, water, guar gum and scrap aluminum.

The various compositions were prepared in the following manner:

Commercial grade carbon tetrachloride was thickened to a thin jelly-like consistency by blending from about 1.5 to about 2 weight percent aluminum oleate or aluminum octoate therewith. A second solution containing about 8.6 weight percent sodium nitrate, about 62.0 weight percent ammonium nitrate and 39.4 weight percent water was prepared. (This solution was prepared to be substantially saturated with respect to the nitrate solute components at about 25 C.) The aqueous nitrate solution was gelled by adding thereto from about 1 to about 1.5 to about 2 weight percent aluminum oleate or alumisolution. The methyl alcohol was used as a carbonaceous fuel source.

The three liquid components were blended to provide a substantially homogeneous mixture. This was stringy in appearance and showed no visible miscibility with water. An additional amount of dry particulate sodium nitrate (crushed prills of from about 12 to about 70 mesh U.S. Standard Sieve) was incorporated into the liquid phase along with particulated scrap aluminum as a fuel. The mixtures were blended to assure tht both the solid nitrates and the particulated aluminum were encompassed by the liquid phase.

A very small amount of saturated aqueous ammonia solution (equivalent to about cubic centimeters ammonia solution per 60 pounds of mix was added to the composition to promote crosslinking of the guar gum.

In all cases the product was soft, pliable, rubbery in appearance and readily deformed on standing to fill and adjust to the contour of the space in which it was stored or confined.

The resulting compositions readily sank through a column of water and immersion tests in both stagnant and flowing water indicated no effect on the intactness of the composition or visible degradation from dissolution of the water soluble ingredients.

The compositions also were found to be nonsensitive either to electric squib initiation or a No. 6 electric blasting cap.

The composition propagated unconfined in a 3% inch diameter carbon when initiated by a 60 gram composition C-3 booster.

About to about pounds of the various products were placed in a 2-gallon steel can; the mix was primed with about a 160 gram Pentolite booster which in turn was initiated by a length of gram per foot Primacord. The can was then sealed leaving one end of the Primacord extending up out of the can, this being attached to a firing line. The sealed charge was lowered to about a 40 foot depth in an 80 foot deep pond of water and initiated.

expressions presented by Robert H. Cole in Underwater Explosions, Princeton University Press, 1948.

Table I, which follows, presents mix composition data as well as explosive results for a number of compositions. For purposes of comparison, a prilled ammonium nitrate (94 weight percent) -fuel oil (6 weight percent) explosive composition was utilized as a control.

Example 2.A number of compositions were prepared and tested in the following manner. About a 1000 gram explosive load was prepared and placed in gram per foot Primacord fuse was inserted into the top of the Table I Composition, Wt. Percent Energies, Keel/gram Shot T 6 Table II Explosive Composition plus booster.

NaNOa (prill) NaNO (crushed prill) CO1.

NaNOa (prill) 1 C01 (gelled) 90 Methyl alcohol. 56 Gummed solution 27. 75 28 O NEtNOs (solid). 30. on (coarse filings). 22. 25 7 0C1. (gelled) 9.53 Methyl Alcohol. 3. 81

ummed solution 19.05 I'IQ NaNO 20. 97 Iron (coarse filln 46. 60

1 U.S. Standard Sieve; about 12 to about 20 mesh.

2 U.S. Standard Sieve; about 12 to about mesh.

3 ASTM designated AZ 3l-B having a nominal composition 01' about 2.5-3.5 weight percent aluminum, 0.71.3 weight percent zinc and about 0.2 weight percent manganese, balance magnesium.

S ution containing about 8.62 weight percent NaNO 62.0 weight percent N H4N0 and about 29.4 weight percent H 0, gelled with about 1.5 weight percent guar gum.

*Base control.

1 Control.

Wt. Density Age N o. Gelled N ltrat NaNO; Al 1 A1 Coarse (1b.) (g./cc.) Shock Bubble Total (hrs) C01 Methanol Soln. Prill Flake Flake M M 14. 2 5. 5 28. 0 28. 7 11. 11. 75 27. 44 1.51 407 584 991 Fresh 14. 2 5. 5 28. 0 28. 7 11. 75 11. 75 27. 50 1. 51 410 600 1. 010 D0 14. 2 5. 5 28. 0 28. 7 11. 75 11. 75 27. 50 l. 51 362 623 985 16. 14. 2 5. 5 28. 0 28. 7 11. 75 ll. 75 28. 06 1. 58 460 680 l. 140 20. 11. 40 4. 55 22. 35. 8 12. 75 12. 75 26. 00 1. 51 188 5-15 733 24. 11. 40 4. 55 22. 80 35. 8 12. 75 12. 75 26.50 1. 51 .300 .605 905 48. 11. 40 4. 55 22. 80 35.8 12. 75 12. 74 26.00 1.47 .333 654 987 72. 12.30 4. 9 24. 5 25. 1 10. 6 l6. 6 25. 50 1.40 471 728 1. 199 Fresh Fertilizer Grade Prilled Ammonium Nitrate-Fuel Oil (Control) 16. 38 -0. 86 .173 .264 D 1 The Al flake had the following characteristics:

Sieve Analysis (U.S. Standard): Pereentsltetaincd on reve -100+325 (trace) Thickness, approx. .005 Bulk density, 0.613 gin/cc. The Al coarse scrap had the following characteristics:

sented in Table II which follows:

Percent Retained on Steve 40+100 Reprelsentative particles showed the iollowi mes 1:

Thickness, 0.01-0.08. Width, 0.01650.5. Length, 0.0165"1.2.

1. An inorganic nitrate explosive composition comprismg;

from about to about 75 weight percent of a mixture of alkali metal nitrate and ammonium nitrate, said mixture containing from about 12 to about 65 weight percent of said alkali metal nitrate and from about 10 to about 83 weight percent of ammonium nitrate based on the total composition weight, and from about 5 to about 25 weight percent of a substantially water immiscible halogenated aliphatic hydrocarbon having a density of at least about 1.2 grams per cubic centimeter.

2. The explosive composition as defined in claim 1 tnd having a combination therewith from about 0.2 to tbout 5 weight percent, based on the Weight of said ialogenated hydrocarbon, of a gelling agent for said halogenated hydrocarbon.

3. The composition as a combination therewith percent, based on the total mix, fuel.

4. The composition as defined in claim 3 and having in combination therewith a particulatcd metal fuel, the amount of said metal fuel at a maximum being that which on a stoichiometric basis reacts with the water and oxygen available in the reaction products upon detonation of the composition.

5. A water resistant inorganic nitrate explosive composition which comprises;

(a) a mixture of alkali metal nitrate and ammonium nitrate dissolved in water, the resulting solution having total nitrate solute in an amount of from about 25 weight percent up to that wherein said solution is saturated with respect to said solute, and the total amount of said alkali metal nitrate and said ammonium nitrate in said solution ranging from about 10 to about 25 weight percent of the total composition weight, a natural gum thickening agent for said solution, said gum being present in an amount of from about 0.25 to about 2.5 percent based on the weight of said solution,

(b) a substantially water immiscible halogenated hydrocarbon having a density greater than about 1.2 grams per cubic centimeter in an amount from about 11 to about 19 weight percent based on the total composition, said halogenated hydrocarbon being thickened with a metal soap in an amount of from about 0.5 to about 2.5 weight percent based on said halogenated hydrocarbon,

(c) from about 4 to about 6 weight percent of a liquid carbonaceous fuel, said fuel being a member selected from the group consisting of petroleum oils, liquid fractions derived from petroleum oils, low

molecular weight alcohols having from 1 to about 5 defined in claim 2 and having from about 4 to about 8 weight of a liquid carbonaceous carbon atoms, low molecular weight ketones and aldehydes having from 2 to about carbon atoms,

low molecular weight ethers having from about 2 to about I' carbon atoms and mixtures thereof,

(d) a member selected from the group consisting of solid particulate sodium nitrate, ammonium nitrate and mixtures thereof, to provide in combination from about 2 0 to about weight percent of the total composition, and

(e) from about 5 to about 35 weight percent particulate aluminum,

said composition being further characterized in having a proportion of alkali metal nitrate to ammonium nitrate based on the total amount of these ingredients present therein of about 4/1 to about l/l and said composition being further characterized in that the total amount of liquid present therein, both aqueous and organic ranges from about 35 to about weight percent of the total composition weight.

6. A water resistant inorganic nitrate based explosive composition which comprises;

(a) on a weight basis from about 11 to about 14 percent carbon tetrachloride, said carbon tetrachloride being thickened with from about 1 /2 to about 2 weight percent of a member selected from the group consisting of aluminum octoate and aluminum oleate, the weight of said member being based on the weight of said carbon tetrachloride,

(b) from about 23 to about 28 percent of an aqueous solution comprising about 8.6 weight percent sodium nitrate, about 62 weight percent ammonium nitrate and about 39.4 weight percent water, said aqueous nitrate solution being gelled with from about 1 to about 1.5 percent guar gum based on the weight of said solution,

(c) from about ((1) from about nitrate and,

(e) from about 23 to about 35 percent particulate aluminum,

the liquid components being blended and having the solid ingredients encompassed therein thereby to provide a water-resistant inorganic nitrate based explosive having a ready deformability and pliability.

4 /2 to about 5 /2 percent methanol, 25 to about 35 percent prilled sodium References Cited by the Examiner UNITED STATES PATENTS 7/1963 Bowkley et al. 5/1965 Royer et al. 

1. AN INORGANIC NITRATE EXPLOSIVE COMPOSITION COMPRISING; FROM ABOUT 95 TO ABOUT 75 WEIGHT PERCENT OF A MIXTURE OF ALKALI METAL NITRATE AND AMMONIUM NITRATE, SAID MIXTURE CONTAINING FROM ABOUT 12 TO ABOUT 65 WEIGHT PERCENT OF SAID ALKALI METAL NITRATE AND FROM ABOUT 10 TO ABOUT 83 WEIGHT PERCENT OF AMMONIUM NITRATE BASED ON THE TOTAL COMPOSITION WEIGHT, AND FROM ABOUT 5 TO ABOUT 25 WEIGHT PERCENT OF A SUBSTANTIALLY WATER IMMISCIBLE HALOGNENATED ALIPHATIC HYDROCARBON HAVING A DENSITY OF AT LEAST ABOUT 1.2 GRAMS PER CUBIC CENTIMETER. 